INTEGRATED GEOPHYSICAL SURVEY IN SABINAS BASIN FOR THE EVALUATION OF DEEP AQUIFERS AND NON-CONVENTIONAL RESOURCES (SHALE GAS)

The Sabinas basin is a complex paleo-element composed by multiple potentially gas-bearing formations. The gas is hosted in a variety of complex geological structures such as folds and faults. Non-conventional resources (in particular shale gas) of the basin have been located in the formations Eagle Ford and La Casita, between 1500 and 4000 meters depth. The large amounts of water required for the gas production together with the low levels of annual precipitation in the region pose a serious problem demanding for the application of geophysical methods for the exploration of deeper groundwater sources.

This paper presents the results of a geophysical survey using Magnetotelluric (MT), Time-Domain Electromagnetic (TDEM) and Passive Seismic (Spatial Autocorrelation Method, SPAC) techniques as complementary tools for the evaluation and identification of geological structures and fracturing conditions in depth, associated with possible deep groundwater reservoirs. The results of these techniques were jointly evaluated with gravimetric and magnetic data in order to improve the recognition of geological structures associated with the tectonic history of the basin.

With a clearly hydrogeological scope, the present study demonstrates the ability to guide local explorations by means of geophysical methods in conjunction with direct information, which in the present study allowed to recognize deep horizons and formations with hydrogeological potential. Also in conjunction with traditional seismic reflection data, the exploration by means of the techniques presented in this work, not only supports the prospecting of water resources, but also contributes complementary information for the detection of non-conventional resources.